open an excel file in c# in csharp

main.cs
using Microsoft.Office.Interop.Excel;

// ...

Application excel = new Application();
Workbook workbook = excel.Workbooks.Open(@"C:\path\to\file.xlsx");
Worksheet worksheet = workbook.ActiveSheet;

// Now you can access the cells and data in the worksheet:
Range range = worksheet.Range["A1"];
string cellValue = (string) range.Value;
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